FOSSIL PLANTS FROM MIOCENE STRATA IN THE HIGH PLAINS: A POTENTIAL BIOSTRATIGRAPHIC CORRELATION TOOL

Among the most abundant fossils found in many Miocene sedimentary deposits in the High Plains are the reproductive and vegetative remains of vascular plants. These remains include three dimensional silicifications and calcifications of fruits, seeds, stems, leaves, and roots of grasses (Poaceae), sedges (Cyperaceae), borages (Boraginaceae), chenopods (Chenopodiaceae), pondweeds (Potamogetonaceae), hackberries and elms (Ulmaceae), walnuts (Juglandaceae), horsetails (Equisetaceae), and a number of unidentified taxa. Nearly all of the fossils exhibit exquisitely preserved macro- and microfeatures that facilitate accurate identifications and comparisons with related fossil and living taxa. Often widespread and abundant both laterally within individual and across superposed stratigraphic units in the deposits, it is not unusual for geologic sections at outcrops throughout the High Plains to yield several hundred to thousands of individual plant fossils representing ten or more distinctive species. At some localities the floras are associated with significant vertebrate faunas. Floras from sites in Colorado, Kansas, Nebraska, Oklahoma, and Texas collected over the last two decades will be described and compared. The nature, variety, abundance, and distribution of the fossil plants in the deposits suggest that they could be an important biostratigraphic tool for correlating and stacking Miocene geologic sections across the High Plains.